Mined-out portions of stopes are often backfilled with tailings (often referred to as “backfill”), pumped into the stope from a mill. As is well known in the art, the tailings typically include substantial amounts of water. Draining the backfill is a difficult task that may take a long time. The undrained water can exert significant pressure on structures at the stope entrances (fill fences). The known practices tend to rely on relatively slow drainage, which results in substantial water pressure exerted against fill fences over extended periods of time.
For instance, a first “panel”, or portion, of the ore may be removed, and the opening left by its removal may be backfilled. Typically, once the backfill has been drained sufficiently and “cured”, a second “panel” of the ore is removed. Subsequent panels may also be removed, sequentially.
As is well known in the art, as an initial step in excavating the first panel, a raise (i.e., an elongate generally vertical opening) is formed at an outer end of the first panel, to provide a blasting void in which the broken ore caused by blasting the first panel is receivable. The raise may be formed by incremental drilling and blasting, or by a raise bore, or by any other conventional means. Driving a raise by conventional means is an extremely expensive and time-consuming process.
A blasting void is an opening into which some of the broken ore is partially directed by the blast. The blasting void is needed due to the rapid increase in volume of the blasted ground of the second panel, upon ignition of the blast.
In conventional mining, one of the first steps in mining the second panel would be to create a blasting void for the second panel. Typically, this is done by creating a substantially vertical void in the solid rock of the second panel (at one side or end of the second panel), by conventional means.
As is well-known in the art, the step of forming the blasting void for each panel is relatively expensive and time-consuming. Once the blasting void for the second panel is created, the second panel may be drilled using conventional drills, to produce a blasting pattern in the second panel designed to blast toward the blasting void. Subsequently, the second panel is blasted, and the broken ore therefrom is removed by conventional mucking methods.
After the broken ore of the second panel has been excavated, the opening created by the removal of the second panel is backfilled. Typically, the process is repeated with respect to a third and possibly further subsequent panels until the stope has been fully excavated.